Results and
discussion
Physico-chemical properties of
nutshells
To observe the microstructural features of the four different types of
nutshells (NSs), Almond Shell (AS), Filbert Shell (FS), Pecan Shell
(PS), and Walnut Shell (WS), SEM analyses were conducted on the inner
surface, outer surface and the cross sections of the samples. The
structure of nutshells reveals a substantial presence of porous tissue
with a homogeneous distribution along the structural matrix. These
porous tissues form perforations across the layers of the shell
facilitating nutrient uptake by allowing the passage of
liquids.[31,32] The ubiquitous distribution of
these perforations throughout the shell structure is confirmed by SEM
imaging shown in Figure 2 and Figure-S 3. Amongst
these four NSs, Almond Shell (AS) and Walnut Shell (WS) exhibit
remarkable uniformity in the distribution and arrangement of the
apertures pattern, with AS demonstrating larger apertures than the WS.
Diameter of these pores ranges from nano to micro scales, traversing
both external and internal surfaces. Filbert Shell (FS), and Pecan Shell
(PS) exhibit a disorganized distribution of pores (Figure 2
(d-i) ), ranging from nano to micro scales, facilitating the passage of
fluids. Thus, the apertures of these four nutshells act as nano and
micro channels for any fluid flow. The configurations of these
micro/nanochannels have a variety of geometry including convergent,
divergent, and parallel geometrics.[31-33]Moreover, the abundance of these perforations amplifies the adsorption
capacity and augment the surface area for solid liquid interactions
enabling faster capillary absorption of water. The composition of
nutshells (NS) is primarily consisting of lignin, cellulose, and
hemicellulose,[34,35] which are rich in hydroxyl
groups, methoxyl, and carbonyl functional
groups.[36] Therefore, NSs demonstrate mostly
hydrophilic and negative surface charges.[37]